Above: Global TEC and L1 range error
What are these?
Affected by solar activity, Total Electron Content (TEC) describes the total number of free electrons present within one square meter between two points (i.e. between the receiver and satellite). The larger the TEC quantity, the longer the delay in a received GNSS signal. This leads to positional errors in GPS readings amounting to tens or even hundreds of meters in severe circumstances.
The maps above shows the latest TEC values, updated every five minutes. Credits: Trimble and NOAA/SWPC
© Copyright Commonwealth of Australia 2018, Bureau of Meteorology
The graphs on this page show ionospheric Scintillation indices from the Darwin station over the last 24 hours, as measured by SWS Ionospheric Scintillation Monitor (ISM) sites. In each graph, the signal from each of the 31 active GPS satellites is shown with a different colour.
Graphs in the left hand column display amplitude scintillation, a measure of the short timescale fluctuation in the signal to noise. This is quantified by the S4 index. Values over ~0.6 indicate strong scintillation which can cause loss of lock on a GPS signal. A scintillation index below 0.3 is unlikely to have any affect on GPS. Amplitude scintillation seen in the Darwin and Weipa scintillation monitors is commonly due to an ionospheric phenomena called “plasma bubbles”.
Data from other stations in northern Australia can be seen by following this link: Australian SWS Ionospheric Scintillation Graphs